Surfaces for passive binding

Passive surfaces have a broad range of applications as they can bind to a variety of biomolecules.

Passive binding is primarily suited for the immobilization of medium to large sized molecules, such as antibodies, which are capable of establishing several contact points. The exact molecular interaction sites are dependent on the specific matching of the biomolecule's structure with the polymer surface structure. A large variety of biomolecules can be immobilized on passive surfaces with good residual activity.

The family of Thermo Scientific passive surfaces vary in their degree of hydrophilicity and are organized into four different sub-groups: hydrophobic, slightly hydrophilic, hydrophilic, and very hydrophilic. A hydrophobic surface functions predominately via hydrophobic binding. As the surface is made more hydrophilic by the incorporation of oxygen containing functional groups, electrostatic interactions can play a greater role in binding, thus influencing which types of biomolecules will bind strongly to the surface.

The schematic above is a representation of the types of biomacromolecules which can be bound to the available modified surfaces. E.g. if a lipid is to be bound the hydrophobic surface PolySorp is most suitable. Based on the physiochemical characteristics of the biomolecule to be immobilized, a surface can be chosen which is appropriate for robust binding. As is indicated in the diagram, MaxiSorp has the widest breadth of applications as it is capable of binding the greatest range of molecules.

The slight hydrophilicity of these plates enhances their ability to bind a diverse range of biomolecules, including glycoproteins, serum-containing samples, and amphoteric molecules such as lipopolysaccarides. With these plates non-specific adsorption of serum-containing samples are reduced and this will improve the signal-to-noise (S/N) ratio and consequently, sensitivity levels.

Optimized to bind high amounts of IgG (polyclonal), these plates are ideal for antibody sandwich assays (e.g., ELISAs). In addition, they show increased binding of many other proteins and biomolecules that possess hydrophilic/hydrophobic characteristics.

FAQs

The following list offers a brief description of the features of Thermo Scientific Nunc products and their specific applications.

Immuno plates, MaxiSorp surface—These plates are designed for solid phase immuno-assays and have a polystyrene surface with high affinity for polar groups and hydrophilic molecules. These 96 well plates are available with flat (F), round (U), or (C) bottom well designs.

Immuno plates, PolySorp surface—These plates have a polystyrene surface which adsorbs fewer polar molecules compared to the MaxiSorp surface and has a high affinity for hydrophobic groups. These 96 well plates are available with flat(F), round (U), or (C) bottom well designs.

Immuno modules—These modules are designed for solid phase immunoassays. The modules are available in 8, 12, or 16 well formats with (F), (U), and (C) bottom well and 8 well BreakApart with (C) bottom well designs. These different formats allow you to choose the style that is appropriate for your assay design. BreakApart modules and LockWell modules can be used for radio-immunoassays.

The following list describes the geometries of wells available for Immuno plates and modules.

Flat bottom (F)—Allows maximum transmission of light. These plates can be read on a monochromatic reader.

Round bottom (U)—This geometry optimizes washing and coating. These plates can be read using a dual-wavelength reader.

”C” bottom (C)—This design of the well is a combination of both flat and round bottoms. Basically, it is a flat-bottomed well with curved edges at the bottom. These plates also can be read using a monochromatic reader combining optimal reading and washing.

StarWell—These wells have a modified “C” shape geometry with eight fins strategically placed at the bottom. This feature increases surface area, allowing more molecules to become immobilized, which reduces incubation times.

MaxiSorp and PolySorp surfaces were developed for immunology assays. The MaxiSorp surface is a modified, highly charged polystyrene surface with high affinity to molecules with polar or hydrophilic groups. The surface has a high binding capacity for proteins, including globular antibodies in proper orientation. Thus, it offers very high sensitivity in double antibody “sandwich” tests. The PolySorp surface is more hydrophobic than the MaxiSorp surface. It has high affinity to molecules of a more hydrophobic character. This surface is particularly suited to non-protein antigens including virus antigens.

Molecules bind to the PolySorp and MaxiSorp surfaces through passive adsorption. Using IgG as a reference molecule and knowing that it is a globular molecule, theoretical calculations indicate that the maximum binding for the MaxiSorp surface, in monolayer, is 650 ng/cm2. For the PolySorp surface, the binding capacity is 220 ng/cm2. A detailed discussion of the principles and calculations is presented in Thermo Scientific Nunc Bulletin No. 6a ‘Principles in Adsorption to Polystyrene’ and Bulletin No. 6b ‘Stability of Thermo Scientific Nunc Immuno MaxiSorp Surfaces’.